A method of transmitting teletext pages as mentioned in the opening paragraph is disclosed in EBU Interim Technical Document SPB 492 "Teletext Specification 625 line television systems", December 1992. Transmission of teletext pages in vertical blanking intervals (VBI) of a television signal is widely used in many countries of the world. Transmission of teletext pages in both the vertical blanking intervals and active video intervals, as is the case here, is often referred to as full-channel teletext transmission.
VBI teletext transmissions typically use 2 to 12 television lines of each vertical blanking interval and offer a page rate of 4 to 24 pages/sec. Full-channel teletext transmissions using all available television lines typically offer a page rate of 600 pages/sec. The access time of a full-channel teletext service is thus smaller, or the number of pages is proportionally larger than that of a VBI teletext service.
A problem of full-channel teletext is that conventional VBI decoders, of which billions have meanwhile been installed, erroneously respond to conventional full-channel teletext transmissions.